RUSSIA is likely to have gathered "valuable intelligence" on Britain's nuclear programme which could put us at risk of attack, senior RAF officials have warned.

Russian planes and ships have made a string of approaches to Britain in recent months

Britain's only sophisticated spy plane has been out of action for five weeks after returning from the Middle East. It is the only one in the RAF fleet, although two more are on order.

This has given opportunities for "intruders" which could "prejudice the security and effectiveness" of Trident, they said.

In a letter to a newspaper, the officers wrote: "The need to reintroduce Maritime Patrol Aircraft (MPA) into the British frontline is now widely recognised.

"With so few naval escorts available, this will be vital if future aircraft carriers are not to be put severely at risk.

"We know that Russian submarines are monitoring the area from which our nuclear missile submarines emerge from the Clyde.

"Without maritime patrol aircraft surveillance, opportunities for intelligence-gathering by such 'intruders' can only prejudice the security and effectiveness of our strategic deterrent.

"Indeed, it would be surprising if valuable intelligence had not already been acquired by the Russian Navy since the Nimrod force was grounded in March 2010."

The letter is signed by Air Marshall Sir John Harris, Air-Vice Marshall George Chesworth, Air-Vice Marshall David Emmerson, Air-Vice Marshall Andrew Roberts and Air Commodore Andrew Neal.

Though less sophisticated their cheaper replacement, the US-built Rivot Joint can still be used to detect vital information about Russian movements in the air and on the sea.

In March, the Commons Defence Committee warned the lack of a maritime patrol aircraft had opened up a "crucial gap" in UK defences.

The committee warned that more aircraft, warships, tanks and missiles were needed to provide a convincing deterrent to further aggression by Russian president Vladimir Putin.

In recent months there have been a string of approaches to Britain by Russian planes and ships.

Two Typhoon fighter jets were launched from RAF Lossiemouth in Scotland to intercept Russian bombers heading towards the UK earlier this month.

And in April, Typhoons out of Lossiemouth again intercepted Bear bombers flying near UK airspace, hours after HMS Argyll was deployed to monitor a destroyer and two other ships from the country as they passed through the English Channel.